1. Technical Field
The present invention relates generally to power conversion, and more particularly to a power conversion apparatus.
2. Description of Related Art
Typically, a conventional power conversion apparatus converts power with a transformer and other electronic components, and while the transformer works, it would generate corresponding magnetizing inductance and leakage energy, wherein leakage energy is a natural phenomenon which happens due to incomplete coupling of magnetic flux between the primary and secondary windings of the transformer. With wider air gap between the primary winding and the secondary winding, the coupling coefficient of the transformer becomes lower, which generates more leakage energy.
In fact, leakage energy of a transformer can be seen as the parasitic inductance of an equivalent parasitic inductor which is in-series connected to an equivalent inductor of the primary winding. Therefore, while a transformer works, the energy stored in the equivalent inductor of the primary winding is transferred to the secondary winding and the loading, but the energy stored in the leakage energy has no circuit path to go, which causes enormous voltage spikes on other components of the circuit. Therefore, there usually is an additional buffer circuit applied in a transformer to absorb and consume the leakage energy. But such buffer circuit may reduce the performance of the transformer.
However, for those power conversion apparatuses applied in wireless power transmission systems, the coupling coefficient would be greatly lowered with wider air gaps, and as a result, there would be much more leakage energy generated. In such cases, the aforementioned design of buffer circuits would not only greatly reduce the performance of the transformer, but also generate great amount of waste heat due to absorbing and consuming the leakage energy. The lifespans of the transformer itself and other components of the circuit tend to be shortened because of high temperature.